Employee Benefit Plans (Net Periodic Benefit Cost (Credit)) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 43	$ 45	$ 127	$ 131
Interest cost		80	82	238	263
Expected return on plan assets		(209)	(197)	(625)	(582)
Amortization of prior service cost (credit)			(1)
Amortization of net actuarial loss		48	58	145	155
Settlements	[1]		3	5	5
Net periodic benefit credit		(38)	(10)	(110)	(28)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost		6	8	18	22
Interest cost		11	15	35	45
Expected return on plan assets		(43)	(39)	(130)	(117)
Amortization of prior service cost (credit)		(11)	(12)	(32)	(37)
Amortization of net actuarial loss		1	1	3	4
Net periodic benefit credit		$ (36)	$ (27)	$ (106)	$ (83)

[1] 2021 amounts relate primarily to the Dominion Energy executive nonqualified pension plan. 2020 amounts related primarily to Dominion Energy’s sale of substantially all of its gas transmission and storage operations to BHE.